<< Chapter < Page Chapter >> Page >
This module explains the method of passive jamming and what effect this method has on a radar's speed dectection .

Passive jammers:

These devices re-radiate the radar signal after distorting it (adding noise and/or shifting frequency) in such a way the true target reflection is masked by the distorted signal. A passive jammer does not generate or amplify a signal, only channel or redirect the radar signal (after distorting) back toward the radar.


  • Legal in most states.


  • Certain states (including California, Utah, Minnesota, Ohio, Indiana and Oklahoma) have laws prohibiting any jamming device
  • The large antennas required to absorb the incident radar beams can actually increase your car’s visibility to radar detectors, allowing them to get a reading from a larger distance than otherwise possible.
  • For this method to work the jammer (distorted signal) power must be as large as or greater than target reflected power -- the jammer antenna would need to capture well over half of all the radar energy striking the target (a very large jammer antenna), and be aligned to the radar antenna. To date all known passive jammers have had no effect on any radar under any circumstances.


Now here is an example of a passive jammer that slightly shifts the frequency of incoming radar. Thus, the reflection from a car equipped with this sort of passive jammer will have three peaks:

This causes the radar detector matched filter to output this:
Thus, the passive jammer has foiled the police without ever transmitting any energy of its own. In this case, the cop incorrectly read the car’s speed as 62 mph, instead of the real 100 mph. However, in practice, a passive jammer NEVER works. The reason for this is that for the passive jammer to work it must reflect over 50% of the light. An example of this is shown below. This is a Passive Jammer which reflects 60% of the light incident on the car:
In this case, the matched filter reads the jammer signal instead of the real Doppler shifted signal. Now, observe what happens when the passive jammer only reflects 40% of the signal incident on the car:
Thus, when the passive jammer only reflects 40% of the incident beam, it does not work at all. The police still correctly read the speed of the car at 100mph. This is summed up by the graph below:
This graph shows that if the passive jammer does not pick up at least 50% of the incoming beam, it does not work at all, the police still correctly read a speed of ~100 mph. Since cars are much larger than the jammer antenna, in practice the passive jammer can never reflect much more than 10% of the incident beam. Thus, passive jammers NEVER work.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Radar jammer in matlab. OpenStax CNX. Dec 23, 2004 Download for free at http://cnx.org/content/col10257/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Radar jammer in matlab' conversation and receive update notifications?